they did not consume alcohol on a regular basis and 23%
claimed to drink alcohol regularly; 36% of workers did not
regularly wear ear-plugs in workplace, 67% worked regular
work on eight-hour schedules and 33% were on 12-hour
work schedules.
A comparison between the type of shift and severity of
hearing loss is shown in Table 2. The 12-hour work schedule
of workers showed a significantly lower level of hearing loss
(LFH, HFH and 4 kHz) in both ears than those who worked
regular eight hours. The severity of hearing loss in the right
ear was slightly higher than that in the left ear.
Table 3 illustrates shift work affect hearing loss using
multiple logistic regressions adjusted for age, smoking
and work duration. The odds ratio (1.88, 1.84 and 1.47) on
hearing loss was higher in the three outcomes (LFH, HFH
and 4 kHz) for those who worked regularly on eight-hour
shifts compared with those who worked the 12-hour work
schedule, but not significantly.
Discussion
Long-term exposure to noise at work causes hearing loss.
Although countermeasures have successfully reduced
noise levels in many industries, noise is still a common
occupational hazard, and noise induced hearing loss is one
of the major occupational diseases worldwide.[11-14] Our
study found that the employees who worked the 12-hours
work schedule suffered a lower degree of hearing loss than
those on the eight-hour shift. Since the group that worked